Video networks communicate audio visual data to allow participants in a video call to see and hear each other even over extended distances. Typically, video endpoints collect video images and audio signals from local participants, digitize the video images and audio signals, and compress the video images and audio signals for transfer over a network to a remote video endpoint. The digitized audio visual data is typically transferred over a number of different types of networks and with a number of different types of protocols and then converted to images and sounds at the remote location by decompressing the data and converting the data into video images and audio signals for presentation at the remote site.
Digitization, compression and decompression functions for transfer of audio and visual data are typically performed with specialized hardware known as CODECs, an abbreviation for compression\decompression. Compressed audio visual data may be sent through networks with equipment having a variety of degrees of specialization. For instance, a simple video teleconference might involve a direct dial up between two video endpoints, such as with an ISDN or T-1 connection. More complex video calls often involve specialized equipment such as multicall units (MCU) that coordinate conferences between three or more endpoints and such as gateway devices that coordinate communication between devices using different protocols. Such specialized devices are deployed in video networks to allow access by video endpoints as needed when a video call is configured and initiated across the video network. Alternatively, in TCP\IP networks that support video and voice over Internet Protocol, the functions of such specialized equipment are typically performed by software modules loaded on servers of the video network.
When a video call is established between video endpoints, the audio visual data is typically not accessible at a packet-level or CODEC-level as the audio visual data is routed between endpoints and through various video devices. Generally, video devices are designed to pass through audio visual data without extensive processing in order to avoid delays in the video conference presentation. For instance, the H.323 video conference protocol enables services such as call forwarding but avoids exposing audio visual data to a packet level or CODEC level as the data passes through the video network nodes. Although compliance with the H.323 protocol aids in establishing and maintaining high quality videoconferences, when quality problems do arise the inaccessibility of audio visual data as the data transfers through the video network makes the diagnosis of the problems difficult.